What is considered over-training in sport and bodybuilding?

Injury: Overtraining might lead to injury and pain. Loss of strength and stamina might also develop. Generally, an overall strengthening program, which includes core strength, flexibility, as well as cardiovascular training will prevent overtraining related problems. Working one particular muscle group too many times each week can also lead to problems - your muscle needs proper recovery time.

Decreased outcomes: Over-training is when you start seeing decreased performance or outcomes even though you are continuing to train harder. You must listen to your body because there does need to be down time or cross-training for the body to heal. Achy pain is fine - but sharp pain is a clue that you are over doing it. Make sure to work on core strength and cross-train.